The present invention relates generally to a method of controlling a carriage and a paper feed in a printer. More particularly, the invention relates to a method of controlling a carriage and a paper feed in a printer, which enables characters to be printed on a substantially full area of a recording medium including the leading or trailing edge thereof without the print head catching on the leading or trailing edge or corners of the recording medium.
A printer generally includes a carriage, a print head mounted on the carriage, a ribbon mask mounted on the carriage, and an ink ribbon which is fed between a recording medium and a print hole formed in the ribbon mask on the front of the print head. Objects, or characters, are printed on the recording medium through the print hole. This type of printer, called a dot matrix printer, is well known in the prior art.
FIGS. 7(a) and 7(b) show a portion of a prior art dot matrix printer and the relationship of a print hole 1 of a ribbon mask and a recording medium 2 in a dot matrix printer. Reference numeral 3 designates wires driven forward out of the head.
In the prior art printer, when the carriage and a paper feed are controlled so that the printing operation starts from the leading end 2b of recording medium 2, a corner part 2a of recording medium 2 may catch in print hole 1 as it advances in the direction of Arrow A. As a result, the recording medium may be broken or the printer may work improperly.
Also in the printer of the type not having the ink ribbon and the ribbon mask, such as an ink jet printer, if corner part 2a of recording medium 2 is curled, the printing operation will progress so that the print head pushes up the curled corner 2a of recording medium 2, and the print head lies under curled corner 2a of recording medium 2.
To prevent print hole 1 from catching corner part 2a of recording medium 2, the conventional art controls the carriage and the paper feed so that the printing operation starts from a position where print hole 1 is located below leading edge 2c of recording medium 2, as shown in FIG. 8. As a result, the following problems are encountered.
As shown in FIG. 8, the upper end of print hole 1 and wire 3a located at the highest position are spaced a distance L from leading edge 2c of recording medium 2. As a result, it is impossible to print characters on the area of recording medium 2 within this distance L of leading edge 2c of recording medium 2. If it is attempted to print a character in this area within the distance L of the leading edge 2c of recording medium 2 using this prior art printer configuration and control, print hole 1 will catch corner part 2a of recording medium 2 as stated above.
The same problem of catching the corner of leading edge 2c of recording medium 2 also arises when trying to print on the trailing edge of recording medium 2.